techpack-video: Variant build support

Added binary artifacts support for variant build

Change-Id: I07e0ebccdc681de9fb2b6f8f135f6f7b28dd1f3e
diff --git a/libaac/Android.mk b/libaac/Android.mk
index 96a7fe2..7669080 100644
--- a/libaac/Android.mk
+++ b/libaac/Android.mk
@@ -1,3 +1,4 @@
+ifeq ($(BUILD_VIDEO_TECHPACK_SOURCE), true)
 LOCAL_PATH := $(call my-dir)
 
 include $(CLEAR_VARS)
@@ -27,3 +28,4 @@
 
 LOCAL_SANITIZE := integer_overflow
 include $(BUILD_SHARED_LIBRARY)
+endif # BUILD_VIDEO_TECHPACK_SOURCE